Well, I was so intrigued that I thought I'd do a little test myself (I hope titrisol will also post his results and/or comment on mine). This is a first series of tests using APX 100 and Rodinal at different temps and dilutions. FWIW, here are some results (sorry, long post ahead).
I shot three series of each five shots of the same subject under the same lighting conditions (overcast, light was stable during shoot which took about only 5 minutes or so). Bracketing was used: +1 stop, +1/2 stop, +-0, -1/2, -1. Light measured with spot meter on grey card (zone V), white wall (zone VII), and a dark hedge (zone III). (I placed the hedge on zone III and the rest fell in the zones as indicated) See attached picture from a digicam.
One series was developed in Rodinal 1+50 at 24°C (75°F) for 18 minutes (i.e. 20 minutes recommended by Agfa -10% because I use a condensor head enlarger-- I usually need to reduce the recomm. dev time by about 20% but since it was overcast and not a very contrasty scene I cut it back by only 10%).
The second series was souped in Rodinal 1+50 at 18°C (65°F) for 10'45" (i.e. 12' recomm. dev time by Agfa -10%).
The third series: Rodinal 1+25 at 18°C (65°F) for 9' (i.e. 10' recomm. -10%).
Agitation: every minute 10 seconds (=5 gentle tilts). Temp constantly monitored (I kept the temp within 0.3°C deviation of the target temp at all times)
Since Agfa recommends these times for the same gamma (contrast index) of 0.55, I thought all series would come out each as contrasty as the others. Not so. The first roll had the most contrast, the second a little less and the last was the least contrasty of all. So, I need to do a second test changing the dev times to arrive at test series with the same contrast index.
These negs were printed on Ilford MGIV RC (glossy) using maximum black test (filter grade 2) to determine print exposure time (determined for each series seperately). Developed in Amaloco AM 1001 print developer for 3'.
The results:
-1+50 24°C (75°F): EI 75; dev time needs to be reduced by about 20% (guess) since zone VII does not print with sufficient detail (more like zone VIII).
-1+50 18°C (65°F): EI 75; dev time needs slight reduction (say 10%) since zone VII could do with a bit more detail
-1+25 18°C: EI 50; dev time is OK, zone VII prints with sufficient detail
The 1+50 18° gives slightly less grainy results than the 1+50 24°C, however, this could be due because the 18° series received less development (judging by the less contrasty negs). I should do another test series trying to arrive at the same contrast index to see if this result remains.
The 1+25 gives considerably more grain than both other test series even though this one was the least developed series (judging by the fact that this series produced the least contrasty negs of them all). So this test indicates that a higher dilution does indeed decrease graininess with Rodinal.
If you guys spot anything wrong with the test procedure (it's not scientific, I know), please post your recommendations! I'll try to improve the test if possible. (I don't have a densitometer in case you're wondering)
When I get the second test series done I'll post an update, but I don't think it'll be for one of these days since Belgian weather has suddenly improved a lot (they're expecting up to 30°C for the following days -- so if you don't mind I'm staying out of the darkroom!
)
dirk
